Outside drain blocked — how to clear it

Lift the drain cover nearest to where the problem is occurring. Use a flat-blade screwdriver or drain cover key. Most covers are heavy — lift carefully.

Look in the chamber: if it's full or overflowing, the blockage is downstream (between this chamber and the next one or the main sewer). If it's empty, the blockage is upstream.

For a blocked downstream section: use drain rods. Screw 2–3 rods together, attach a corkscrew plunger head, and push into the downstream pipe while turning clockwise. Turning keeps the rods screwed together — turning anticlockwise will unscrew them in the pipe.

Work the rods back and forth with a firm pushing and twisting motion. You'll feel resistance at the blockage. Break through it and the chamber should start to drain.

Once the drain starts flowing, use a plunger head on the rods to push remaining debris through, then run a hosepipe on full pressure into the drain to flush everything through.

For a blocked upstream section (chamber is empty but a fixture above isn't draining): find the upstream chamber or access the pipe near the blocked fixture and rod downstream toward the chamber.

If you cannot clear the blockage with rods, or if you are concerned about root intrusion or pipe damage, call a drainage professional. Forcing rods too hard can damage fragile clay pipes.